Fabrication methods for batteries

ABSTRACT

A method may involve forming a first electrode on a structure, where the first electrode defines an anode of a battery, and where the battery is configured to provide electrical power to a circuit located on the structure. The method may further involve forming a second electrode on the structure, where the second electrode defines a cathode of the battery, and where the second electrode is configured to reduce oxygen. And the method may involve embedding the structure in a polymer.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

A body-mountable device may be configured to monitor health-relatedinformation based on at least one analyte from a user. For example, abio-compatible device may be embedded in a polymer to provide thebody-mountable device. The bio-compatible device includes a sensorconfigured to detect the at least one analyte (e.g., glucose) in a fluidof a user wearing the body-mountable device. The body-mountable devicemay also be configured to monitor various other types of health-relatedinformation.

SUMMARY

In one aspect, a method involves: forming a first electrode on astructure, where the first electrode defines an anode of a battery, andwhere the battery is configured to provide electrical power to a circuitlocated on the structure; forming a second electrode on the structure,where the second electrode defines a cathode of the battery, and wherethe second electrode is configured to reduce oxygen; and embedding thestructure in a polymer.

In another aspect, a device is disclosed. The device includes a firstpolymer layer defining a first side of the device; a second polymerlayer defining a second side of the device; and a structure between thefirst and second polymer layers, where the structure comprises: a firstelectrode, where the first electrode defines an anode of a battery,where the battery is configured to provide electrical power to a circuitlocated on the structure, and a second electrode, where the secondelectrode defines a cathode of the battery, and where the secondelectrode is configured to reduce oxygen.

In yet another aspect, a system is disclosed. The system includes: meansfor forming a first electrode on a structure, where the first electrodedefines an anode of a battery, and where the battery is configured toprovide electrical power to a circuit located on the structure; meansfor forming a second electrode on the structure, where the secondelectrode defines a cathode of the battery, and where the secondelectrode is configured to reduce oxygen; and means for embedding thestructure in a polymer.

These as well as other aspects, advantages, and alternatives, willbecome apparent to those of ordinary skill in the art by reading thefollowing detailed description, with reference where appropriate to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system with an eye-mountable device inwireless communication with an external reader, according to an exampleembodiment.

FIG. 2a is a top view of an eye-mountable device, according to anexample embodiment.

FIG. 2b is a side view of an eye-mountable device, according to anexample embodiment.

FIG. 2c is a side cross-section view of the eye-mountable device of FIG.2a while mounted to a corneal surface of the eye, according to anexample embodiment.

FIG. 2d is a side cross-section view showing the tear film layerssurrounding the surfaces of the eye-mountable device mounted as shown inFIG. 2c , according to an example embodiment.

FIGS. 3a-d show stages of fabricating a battery, according to an exampleembodiment.

FIGS. 4a-d show stages of forming an electrode, according to an exampleembodiment.

FIG. 5 depicts an example structure, according to an example embodiment.

FIG. 6 depicts an example body-mountable device, according to an exampleembodiment.

FIG. 7 is a flow chart illustrating a method for fabricating a battery,according to an example embodiment.

FIG. 8 is a flow chart illustrating a method for forming an electrode,according to an example embodiment.

FIG. 9 depicts a computer-readable medium configured according to anexample embodiment.

DETAILED DESCRIPTION

The following detailed description describes various features andfunctions of the disclosed methods and systems with reference to theaccompanying figures. In the figures, similar symbols typically identifysimilar components, unless context dictates otherwise. The illustrativemethod and system embodiments described herein are not meant to belimiting. It will be readily understood that certain aspects of thedisclosed methods and systems can be arranged and combined in a widevariety of different configurations, all of which are contemplatedherein.

I. INTRODUCTION

A body-mountable device may be configured to monitor health-relatedinformation based on at least one analyte detected in a fluid of a userwearing the body-mountable device. Such a body-mountable device mayinclude a structure embedded in a polymer that includes a sensorconfigured to detect the at least one analyte.

The structure may further include a circuit and a battery. The batterymay be configured to provide electrical power to the circuit.Beneficially, the battery may reduce or eliminate the need for one ormore power scavenging systems on the structure, such as an energyharvesting antenna that may capture energy from incident radio frequencyradiation or one or more solar cells that may capture energy fromincoming ultraviolet, visible, and/or infrared radiation. With thisarrangement, the battery may permit autonomous operation of thebody-mountable device.

For example, the circuit may include an electrochemical sensor andpotentiostat, and the battery may bias the electrochemical sensor viathe potentiostat. As another example, the circuit may include a memoryand the battery may power the memory for data logging of sensorreadings. The battery may also be configured to provide electrical powerto a variety of other circuits that may be located on the structure,such as a computation circuit, a communication circuit, and/or a displaycircuit. Further, in some implementations, the battery may be configuredto provide electrical power to one or more low-power circuits.

In addition, the battery may also be configured to provide electricalpower to other components located on the structure. As one example, thebattery may be configured to provide electrical power to one or moreindicators located on the structure, such a pixel array. With thisarrangement, the one or more indicators may be configured to providefeedback to a wearer of the body-mountable device. As another example,the battery may be configured to provide electrical power to a cameraand/or a video camera that may be located on the structure. Further, insome implementations, the battery may be configured to provideelectrical power to one or more peripheral components.

Disclosed herein are fabrication methods for batteries that may beincluded in the body-mountable device. Beneficially, embodimentsdescribed herein may provide batteries that may be biocompatible andnontoxic. Further, embodiments described herein may provide batteriesthat may be flexible and may conform to the structure.

II. EXAMPLE SYSTEMS AND DEVICES

An example body-mountable device that comprises an eye-mountable devicethat is configured to detect at least one analyte in a tear film of auser wearing the eye-mountable device will now be described in greaterdetail.

A structure in accordance with an exemplary embodiment may include asensor, electronics, a battery, and an antenna all situated on asubstrate. The battery may be configured to provide electrical power tothe electronics. And the electronics may operate the sensor to performreadings and operate the antenna to wirelessly communicate the readingsfrom the sensor to an external reader via the antenna. The sensor can bearranged on the substrate to face outward, away from the corneal surfaceof the user, so as to generate clinically relevant readings from tearfluid of the user that the sensor receives via a channel in the anteriorside of the eye-mountable device. For example, the sensor can besuspended in the lens material and situated such that the sensor is lessthan 10 micrometers from the anterior edge of the eye-mountable device.The sensor can generate an output signal indicative of a concentrationof an analyte that the sensor receives via the channel.

FIG. 1 is a block diagram of a system 100 with an eye-mountable device110 in wireless communication with an external reader 180. The exposedregions of the eye-mountable device 110 are made of a polymeric material120 formed to be contact-mounted to a corneal surface of an eye. Inaccordance with the exemplary methods, polymeric material 120 maycomprise a first polymer layer and a second polymer layer.

Substrate 130 is embedded in the polymeric material 120 to provide amounting surface for a power supply 140, a controller 150,bio-interactive electronics 160, and an antenna 170. The bio-interactiveelectronics 160 are operated by the controller 150. The power supply 140supplies operating voltages to the controller 150 and/or thebio-interactive electronics 160. The antenna 170 is operated by thecontroller 150 to communicate information to and/or from theeye-mountable device 110. The antenna 170, the controller 150, the powersupply 140, and the bio-interactive electronics 160 can all be situatedon the embedded substrate 130. Because the eye-mountable device 110includes electronics and is configured to be contact-mounted to an eye,it may also be referred to as an ophthalmic electronics platform.

To facilitate contact-mounting, the polymeric material 120 can have aconcave surface configured to adhere (“mount”) to a moistened cornealsurface (e.g., by capillary forces with a tear film coating the cornealsurface). Additionally or alternatively, the eye-mountable device 110can be adhered by a vacuum force between the corneal surface and thepolymeric material due to the concave curvature. While mounted with theconcave surface against the eye, the anterior or outward-facing surfaceof the polymeric material 120 can have a convex curvature that is formedto not interfere with eye-lid motion while the eye-mountable device 110is mounted to the eye. For example, the polymeric material 120 can be asubstantially transparent curved polymeric disk shaped similarly to acontact lens.

The polymeric material 120 can include one or more biocompatiblematerials, such as those employed for use in contact lenses or otherophthalmic applications involving direct contact with the cornealsurface. The polymeric material 120 can optionally be formed in partfrom such biocompatible materials or can include an outer coating withsuch biocompatible materials. The polymeric material 120 can includematerials configured to moisturize the corneal surface, such ashydrogels and the like. In some instances, the polymeric material 120can be a deformable (“non-rigid”) material to enhance wearer comfort. Insome instances, the polymeric material 120 can be shaped to provide apredetermined, vision-correcting optical power, such as can be providedby a contact lens.

The substrate 130 includes one or more surfaces suitable for mountingthe bio-interactive electronics 160, the controller 150, the powersupply 140, and the antenna 170. The substrate 130 can be employed bothas a mounting platform for chip-based circuitry (e.g., by flip-chipmounting) and/or as a platform for patterning conductive materials(e.g., gold, platinum, palladium, titanium, copper, aluminum, silver,metals, other conductive materials, combinations of these, etc.) tocreate electrodes, interconnects, antennae, etc. In some embodiments,substantially transparent conductive materials (e.g., indium tin oxide)can be patterned on the substrate 130 to form circuitry, electrodes,etc. For example, the antenna 170 can be formed by depositing a patternof gold or another conductive material on the substrate 130. Similarly,interconnects 151, 157 between the controller 150 and thebio-interactive electronics 160, and between the controller 150 and theantenna 170, respectively, can be formed by depositing suitable patternsof conductive materials on the substrate 130. A combination of resists,masks, and deposition techniques can be employed to pattern materials onthe substrate 130.

The substrate 130 can be a relatively rigid polymeric material, such asPET, paralyene or another material sufficient to structurally supportthe circuitry and/or electronics within the polymeric material 120. Theeye-mountable device 110 can alternatively be arranged with a group ofunconnected substrates rather than a single substrate. For example, thecontroller 150 and a bio-sensor or other bio-interactive electroniccomponent can be mounted to one substrate, while the antenna 170 ismounted to another substrate and the two can be electrically connectedvia the interconnects 157.

In some embodiments, the bio-interactive electronics 160 (and thesubstrate 130) can be positioned away from the center of theeye-mountable device 110 and thereby avoid interference with lighttransmission to the eye through the center of the eye-mountable device110. For example, where the eye-mountable device 110 is shaped as aconcave-curved disk, the substrate 130 can be embedded around theperiphery (e.g., near the outer circumference) of the disk. In someembodiments, the bio-interactive electronics 160 (and the substrate 130)can be positioned in the center region of the eye-mountable device 110.The bio-interactive electronics 160 and/or the substrate 130 can besubstantially transparent to incoming visible light to mitigateinterference with light transmission to the eye. Moreover, in someembodiments, the bio-interactive electronics 160 can include a pixelarray 164 that emits and/or transmits light to be perceived by the eyeaccording to display driver instructions. Thus, the bio-interactiveelectronics 160 can optionally be positioned in the center of theeye-mountable device so as to generate perceivable visual cues to awearer of the eye-mountable device 110, such as by displayinginformation via the pixel array 164.

The substrate 130 can be shaped as a flattened ring with a radial widthdimension sufficient to provide a mounting platform for the embeddedelectronics components. The substrate 130 can have a thicknesssufficiently small to allow the substrate 130 to be embedded in thepolymeric material 120 without influencing the profile of theeye-mountable device 110. The substrate 130 can have a thicknesssufficiently large to provide structural stability suitable forsupporting the electronics mounted thereon. For example, the substrate130 can be shaped as a ring with a diameter of about 10 millimeters, aradial width of about 1 millimeter (e.g., an outer radius 1 millimeterlarger than an inner radius), and a thickness of about 50 micrometers.The substrate 130 can optionally be aligned with the curvature of theanterior side of the eye-mountable device 110.

The power supply 140 is configured to power the controller 150 andbio-interactive electronics 160. For example, a radio-frequency energyharvesting antenna 142 can capture energy from incident radio radiation.Additionally or alternatively, solar cell(s) 144 (“photovoltaic cells”)can capture energy from incoming ultraviolet, visible, and/or infraredradiation. Furthermore, an inertial power scavenging system can beincluded to capture energy from ambient vibrations. The energyharvesting antenna 142 can optionally be a dual-purpose antenna that isalso used to communicate information to the external reader 180. Thatis, the functions of the antenna 170 and the energy harvesting antenna142 can be accomplished with the same physical antenna.

In addition, the power supply 140 may include a battery 146. The battery146 may comprise an electrolyte and two electrodes, an anode and acathode. Electrochemical reactions between the anode and the electrolyteand between the electrolyte and the cathode can cause the development ofan electrical potential between the electrodes. Further, the battery 146may comprise a solid-state device. In some examples, the battery 146 maybe a re-chargeable battery. In other examples, the battery 146 may be asingle-use battery. In some examples, the battery 146 may be connectedto the controller 150 and/or the antenna 170 via interconnects (notshown).

A rectifier/regulator 148 can be used to condition the captured energyto a stable DC supply voltage 141 that is supplied to the controller150. For example, the energy harvesting antenna 142 can receive incidentradio frequency radiation. Varying electrical signals on the leads ofthe antenna 142 are output to the rectifier/regulator 148. Therectifier/regulator 148 rectifies the varying electrical signals to a DCvoltage and regulates the rectified DC voltage to a level suitable foroperating the controller 150. Additionally or alternatively, outputvoltage from the solar cell(s) 144 can be regulated to a level suitablefor operating the controller 150. The rectifier/regulator 148 caninclude one or more energy storage devices arranged to mitigate highfrequency variations in the ambient energy harvesting antenna 142 and/orsolar cell(s) 144. For example, an energy storage device (e.g.,capacitor, inductor, etc.) can be connected to the output of therectifier/regulator 148 so as to function as a low-pass filter. Inaddition, the rectifier/regulator 148 could provide a DC supply voltage141 from the battery 146. In some embodiments, the rectifier/regulator148 could generate a voltage used to recharge the battery 146. With thisarrangement, captured energy from the energy-harvesting antenna 142,solar cell(s), and/or the inertial power scavenging system may be usedto recharge the battery 146.

The controller 150 is turned on when the DC supply voltage 141 isprovided to the controller 150, and the logic in the controller 150operates the bio-interactive electronics 160 and the antenna 170. Thecontroller 150 can include logic circuitry configured to operate thebio-interactive electronics 160 so as to interact with a biologicalenvironment of the eye-mountable device 110. The interaction couldinvolve the use of one or more components, such as an analyte bio-sensor162, in bio-interactive electronics 160 to obtain input from thebiological environment. Alternatively or additionally, the interactioncould involve the use of one or more components, such as the pixel array164, to provide an output to the biological environment.

In one example, a sensor interface module 152 can be included foroperating the analyte bio-sensor 162. The analyte bio-sensor 162 can be,for example, an amperometric electrochemical sensor that includes aworking electrode and a reference electrode. Application of anappropriate voltage between the working and reference electrodes cancause an analyte to undergo electrochemical reactions (e.g., reductionand/or oxidation reactions) at the working electrode to generate anamperometric current. The amperometric current can be dependent on theanalyte concentration, and thus the amount of amperometric current canprovide an indication of analyte concentration. In some embodiments, thesensor interface module 152 can be a potentiostat configured to apply avoltage difference between the working and reference electrodes whilemeasuring a current through the working electrode.

In some instances, a reagent can also be included to sensitize theelectrochemical sensor to desired analytes. For example, a layer ofglucose oxidase (“GOX”) can be situated around the working electrode tocatalyze glucose into hydrogen peroxide (H₂O₂). The hydrogen peroxidecan then be oxidized at the working electrode, which releases electronsto the working electrode, which generates a current.

The current generated by either reduction or oxidation reactions can beapproximately proportionate to the reaction rate. Further, the reactionrate can be dependent on the rate of analyte molecules reaching theelectrochemical sensor electrodes to fuel the reduction or oxidationreactions, either directly or catalytically through a reagent. In asteady state, where analyte molecules diffuse to the electrochemicalsensor electrodes from a sampled region at approximately the same ratethat additional analyte molecules diffuse to the sampled region fromsurrounding regions, the reaction rate can be approximatelyproportionate to the concentration of the analyte molecules. The currentcan thus provide an indication of the analyte concentration.

The controller 150 can optionally include a display driver module 154for operating the pixel array 164. The pixel array 164 can be an arrayof separately programmable light transmitting, light reflecting, and/orlight emitting pixels arranged in rows and columns. The individual pixelcircuits can optionally include liquid crystal technologies,microelectromechanical technologies, emissive diode technologies, etc.to selectively transmit, reflect, and/or emit light according toinformation from the display driver module 154. Such a pixel array 164can also optionally include more than one color of pixels (e.g., red,green, and blue pixels) to render visual content in color. The displaydriver module 154 can include, for example, one or more data linesproviding programming information to the separately programmed pixels inthe pixel array 164 and one or more addressing lines for setting groupsof pixels to receive such programming information. Such a pixel array164 situated on the eye can also include one or more lenses to directlight from the pixel array to a focal plane perceivable by the eye. Insome embodiments, the battery 146 may be configured to provideelectrical power to the pixel array 164.

The controller 150 can also include a communication circuit 156 forsending and/or receiving information via the antenna 170. Thecommunication circuit 156 can optionally include one or moreoscillators, mixers, frequency injectors, etc. to modulate and/ordemodulate information on a carrier frequency to be transmitted and/orreceived by the antenna 170. In some examples, the eye-mountable device110 is configured to indicate an output from a bio-sensor by modulatingan impedance of the antenna 170 in a manner that is perceivable by theexternal reader 180. For example, the communication circuit 156 cancause variations in the amplitude, phase, and/or frequency ofbackscatter radiation from the antenna 170, and such variations can bedetected by the external reader 180.

The controller 150 is connected to the bio-interactive electronics 160via interconnects 151. For example, where the controller 150 includeslogic elements implemented in an integrated circuit to form the sensorinterface module 152 and/or display driver module 154, a patternedconductive material (e.g., gold, platinum, palladium, titanium, copper,aluminum, silver, metals, combinations of these, etc.) can connect aterminal on the chip to the bio-interactive electronics 160. Similarly,the controller 150 is connected to the antenna 170 via interconnects157.

It is noted that the block diagram shown in FIG. 1 is described inconnection with functional modules for convenience in description.However, embodiments of the eye-mountable device 110 can be arrangedwith one or more of the functional modules (“sub-systems”) implementedin a single chip, integrated circuit, and/or physical feature. Forexample, while the rectifier/regulator 148 is illustrated in the powersupply block 140, the rectifier/regulator 148 can be implemented in achip that also includes the logic elements of the controller 150 and/orother features of the embedded electronics in the eye-mountable device110. Thus, the DC supply voltage 141 that is provided to the controller150 from the power supply 140 can be a supply voltage that is providedon a chip by rectifier and/or regulator components of the same chip.That is, the functional blocks in FIG. 1 shown as the power supply block140 and controller block 150 need not be implemented as separatedmodules. Moreover, one or more of the functional modules described inFIG. 1 can be implemented by separately packaged chips electricallyconnected to one another.

Additionally or alternatively, the energy harvesting antenna 142 and theantenna 170 can be implemented with the same physical antenna. Forexample, a loop antenna can both harvest incident radiation for powergeneration and communicate information via backscatter radiation.

The external reader 180 includes an antenna 188 (or group of more thanone antennae) to send and receive wireless signals 171 to and from theeye-mountable device 110. The external reader 180 also includes acomputing system with a processor 186 in communication with a memory182. The memory 182 is a non-transitory computer-readable medium thatcan include, without limitation, magnetic disks, optical disks, organicmemory, and/or any other volatile (e.g., RAM) or non-volatile (e.g.,ROM) storage system readable by the processor 186. The memory 182 caninclude a data storage 183 to store indications of data structures, suchas sensor readings (e.g., from the analyte bio-sensor 162), programsettings (e.g., to adjust behavior of the eye-mountable device 110and/or external reader 180), etc. The memory can also include programinstructions 184 for execution by the processor 186 to cause theexternal reader to perform processes specified by the programinstructions 184. For example, the program instructions 184 can causeexternal reader 180 to provide a user interface that allows forretrieving information communicated from the eye-mountable device 110(e.g., sensor outputs from the analyte bio-sensor 162). The externalreader 180 can also include one or more hardware components foroperating the antenna 188 to send and receive the wireless signals 171to and from the eye-mountable device 110. For example, oscillators,frequency injectors, encoders, decoders, amplifiers, filters, etc. candrive the antenna 188 according to instructions from the processor 186.

The external reader 180 can be a smart phone, digital assistant, orother portable computing device with wireless connectivity sufficient toprovide the wireless communication link 171. The external reader 180 canalso be implemented as an antenna module that can be plugged into aportable computing device, such as in an example where the communicationlink 171 operates at carrier frequencies not commonly employed inportable computing devices. In some instances, the external reader 180is a special-purpose device configured to be worn relatively near awearer's eye to allow the wireless communication link 171 to operatewith a low power budget. For example, the external reader 180 can beintegrated in eyeglasses, integrated in a piece of jewelry such as anecklace, earring, etc., or integrated in an article of clothing wornnear the head, such as a hat, headband, etc.

In an example where the eye-mountable device 110 includes an analytebio-sensor 162, the system 100 can be operated to monitor the analyteconcentration in tear film on the surface of the eye. Thus, theeye-mountable device 110 can be configured as a platform for anophthalmic analyte bio-sensor. The tear film is an aqueous layersecreted from the lacrimal gland to coat the eye. The tear film is incontact with the blood supply through capillaries in the structure ofthe eye and includes many biomarkers found in blood that are analyzed tocharacterize a person's health condition(s). For example, the tear filmincludes glucose, calcium, sodium, cholesterol, potassium, otherbiomarkers, etc. The biomarker concentrations in the tear film can besystematically different than the corresponding concentrations of thebiomarkers in the blood, but a relationship between the twoconcentration levels can be established to map tear film biomarkerconcentration values to blood concentration levels. For example, thetear film concentration of glucose can be established (e.g., empiricallydetermined) to be approximately one tenth the corresponding bloodglucose concentration. Thus, measuring tear film analyte concentrationlevels provides a non-invasive technique for monitoring biomarker levelsin comparison to blood sampling techniques performed by lancing a volumeof blood to be analyzed outside a person's body. Moreover, theophthalmic analyte bio-sensor platform disclosed here can be operatedsubstantially continuously to enable real time monitoring of analyteconcentrations.

To perform a reading with the system 100 configured as a tear filmanalyte monitor, the external reader 180 can emit radio frequencyradiation 171 that is harvested to power the eye-mountable device 110via the power supply 140. Radio frequency electrical signals captured bythe energy harvesting antenna 142 (and/or the antenna 170) are rectifiedand/or regulated in the rectifier/regulator 148 and a regulated DCsupply voltage 147 is provided to the controller 150. The radiofrequency radiation 171 thus turns on the electronic components withinthe eye-mountable device 110. Once turned on, the controller 150operates the analyte bio-sensor 162 to measure an analyte concentrationlevel. For example, the sensor interface module 152 can apply a voltagebetween a working electrode and a reference electrode in the analytebio-sensor 162 sufficient to cause the analyte to undergo anelectrochemical reaction at the working electrode. The current throughthe working electrode can be measured to provide the sensor outputindicative of the analyte concentration. The controller 150 can operatethe antenna 170 to communicate the sensor results back to the externalreader 180 (e.g., via the communication circuit 156). The sensor resultcan be communicated by, for example, modulating an impedance of theantenna 170 such that the modulation in impedance is detected by theexternal reader 180. The modulation in antenna impedance can be detectedby, for example, backscatter radiation from the antenna 170.

In some embodiments, the system 100 can operate to non-continuously(“intermittently”) supply energy to the eye-mountable device 110 topower the on-board controller 150 and electronics 160. For example,radio frequency radiation 171 can be supplied to power the eye-mountabledevice 110 long enough to carry out a tear film analyte concentrationmeasurement and communicate the results. For example, the supplied radiofrequency radiation can provide sufficient power to charge twoelectrodes to a potential sufficient to induce electrochemicalreactions, measure the resulting amperometric current, and modulate theantenna impedance to adjust the backscatter radiation in a mannerindicative of the measured current. In such an example, the suppliedradio frequency radiation 171 can be considered an interrogation signalfrom the external reader 180 to the eye-mountable device 110 to requesta measurement. By periodically interrogating the eye-mountable device110 (e.g., by supplying radio frequency radiation 171 to temporarilyturn the device on) and storing the sensor results (e.g., via the datastorage 183), the external reader 180 can accumulate a set of analyteconcentration measurements over time without continuously powering theeye-mountable device 110.

In addition, the radio frequency radiation 171 may be supplied to chargethe battery 146. In some examples, the supplied radio frequencyradiation 171 can charge the battery 146 long enough so that the battery146 is fully charged. Further, in some examples, the supplied radiofrequency radiation 171 can charge so that the battery 146 is less thanfully charged.

Further, in some embodiments, the battery 146 may provide power to thecontroller 150 to operate the analyte bio-sensor 162 to measure ananalyte concentration level. And in at least one such embodiment, thebattery 146 may reduce or eliminate the need for continuous radiofrequency radiation 171 from the external reader 180. With thisarrangement, the battery 146 may permit autonomous operation of theeye-mountable device 110. For example, the battery 146 may bias theanalyte bio-sensor 162, via a potentiostat, so that electrodes in theanalyte bio-sensor 162 are at appropriate potentials for analytemeasurement. As another example, the battery 146 may power a memory inthe controller 150, for data logging of sensor readings from analytebio-sensor 162.

FIG. 2a is a top view of an eye-mountable electronic device 210. FIG. 2bis a side view of the eye-mountable electronic device shown in FIG. 2a .It is noted that relative dimensions in FIGS. 2a and 2b are notnecessarily to scale, but have been rendered for purposes of explanationonly in describing the arrangement of the eye-mountable electronicdevice 210. The eye-mountable device 210 is formed of a polymericmaterial 220 shaped as a curved disk. The polymeric material 220 can bea substantially transparent material to allow incident light to betransmitted to the eye while the eye-mountable device 210 is mounted tothe eye. The polymeric material 220 can be a biocompatible materialsimilar to those employed to form vision correction and/or cosmeticcontact lenses in optometry, such as PET, polymethyl methacrylate(“PMMA”), silicone hydrogels, combinations of these, etc. The polymericmaterial 220 can be formed with one side having a concave surface 226suitable to fit over a corneal surface of an eye. The opposing side ofthe disk can have a convex surface 224 that does not interfere witheyelid motion while the eye-mountable device 210 is mounted to the eye.A circular outer side edge 228 connects the concave surface 224 andconvex surface 226.

The eye-mountable device 210 can have dimensions similar to a visioncorrection and/or cosmetic contact lenses, such as a diameter ofapproximately 1 centimeter, and a thickness of about 0.1 to about 0.5millimeters. However, the diameter and thickness values are provided forexplanatory purposes only. In some embodiments, the dimensions of theeye-mountable device 210 can be selected according to the size and/orshape of the corneal surface and/or the scleral surface of the wearer'seye.

While the eye-mountable device 210 is mounted in an eye, the convexsurface 224 (i.e., the anterior surface) faces outward to the ambientenvironment while the concave surface 226 (i.e., the posterior surface)faces inward, toward the corneal surface. The convex surface 224 cantherefore be considered an outer, top surface of the eye-mountabledevice 210 whereas the concave surface 226 can be considered an inner,bottom surface. The “top” view shown in FIG. 2a is facing the convexsurface 224.

A substrate 230 is embedded in the polymeric material 220. The substrate230 can be embedded to be situated along the outer periphery 222 of thepolymeric material 220, away from the center region 221. The substrate230 does not interfere with vision because it is too close to the eye tobe in focus and is positioned away from the center region 221 whereincident light is transmitted to the light-sensing portions of the eye.Moreover, the substrate 230 can be formed of a transparent material tofurther mitigate any effects on visual perception.

The substrate 230 can be shaped as a flat, circular ring (e.g., a diskwith a central hole). The flat surface of the substrate 230 (e.g., alongthe radial width) is a platform for mounting electronics such as chips(e.g., via flip-chip mounting) and for patterning conductive materials(e.g., via deposition techniques) to form electrodes, antenna(e), and/orconnections. The substrate 230 and the polymeric material 220 can beapproximately cylindrically symmetric about a common central axis. Thesubstrate 230 can have, for example, a diameter of about 10 millimeters,a radial width of about 1 millimeter (e.g., an outer radius 1 millimetergreater than an inner radius), and a thickness of about 50 micrometers.However, these dimensions are provided for example purposes only. Thesubstrate 230 can be implemented in a variety of different form factors.

A loop antenna 270, a controller 250, a battery 255, and bio-interactiveelectronics 260 are disposed on the embedded substrate 230. Thecontroller 250 can be a chip including logic elements configured tooperate the bio-interactive electronics 260 and the loop antenna 270.The controller 250 is electrically connected to the loop antenna 270 byinterconnects 257A also situated on the substrate 230. Similarly, thecontroller 250 is electrically connected to the bio-interactiveelectronics 260 by interconnects 251A.

The battery 255 may be configured to power the controller 250. Thebattery 255 may be electrically connected to the controller 250 byinterconnects 251B. Further, in some such examples, the battery 255 maybe electrically connected to the loop antenna 270 by interconnects 257B.

The interconnects 251A, 251B, 257A, and 257B, the loop antenna 270, thebattery 255, and any conductive electrodes (e.g., for an electrochemicalanalyte bio-sensor, etc.) can be formed from conductive materialspatterned on the substrate 230 by a process for precisely patterningsuch materials, such as deposition or lithography. The conductivematerials patterned on the substrate 230 can be, for example, gold,platinum, palladium, titanium, carbon, aluminum, copper, silver,silver-chloride, and/or other materials.

With reference to FIG. 2a , which is a view facing the convex surface224 of the eye-mountable device 210, the bio-interactive electronics 260is mounted to a side of the substrate 230 facing the convex surface 224.Where the bio-interactive electronics 260 includes an analytebio-sensor, for example, mounting such a bio-sensor on the substrate 230facing the convex surface 224 allows the bio-sensor to receive analyteconcentrations in tear film through a channel 272 in the polymericmaterial 220 to the convex surface 224 (as illustrated in FIGS. 2c and2d ).

Similarly, as shown in FIG. 2a , the battery 255 is mounted to a side ofthe substrate 230 facing the convex surface 224. Where the battery 255includes one or more electrodes that are configured to use as anelectrolyte the tear film, mounting such a battery on the substrate 230facing the convex surface 224 allows the battery 255 to receive the tearfilm through a channel 274 in the polymeric material 220 to the convexsurface 224 (as illustrated in FIGS. 2c and 2d ).

In some embodiments, some electronic components can be mounted on oneside of the substrate 230, while other electronic components are mountedto the opposing side, and connections between the two can be madethrough conductive materials passing through the substrate 230.

The loop antenna 270 is a layer of conductive material patterned alongthe flat surface of the substrate to form a flat conductive ring. Insome instances, the loop antenna 270 can be formed without making acomplete loop. For instance, the loop antenna 270 can have a cutout toallow room for the controller 250, the battery 255, and thebio-interactive electronics 260, as illustrated in FIG. 2a . However,the loop antenna 270 can also be arranged as a continuous strip ofconductive material that wraps entirely around the flat surface of thesubstrate 230 one or more times. For example, a strip of conductivematerial with multiple windings can be patterned on the side of thesubstrate 230 opposite the controller 250, the battery 255, and thebio-interactive electronics 260. Interconnects between the ends of sucha wound antenna (e.g., the antenna leads) can be passed through thesubstrate 230 to the controller 250 and/or the battery 255. In someembodiments, the loop antenna can include a plurality of conductiveloops spaced apart from each other, such as three conductive loops, fiveconductive loops, nine conductive loops, etc. With such an arrangement,the polymeric material 220 may extend between adjacent conductive loopsin the plurality of conductive loops.

FIG. 2c is a side cross-section view of the eye-mountable electronicdevice 210 while mounted to a corneal surface 284 of an eye 280. FIG. 2dis a close-in side cross-section view enhanced to show tear film layers290, 292 surrounding the exposed surfaces 224, 226 of the eye-mountabledevice 210. It is noted that relative dimensions in FIGS. 2c and 2d arenot necessarily to scale, but have been rendered for purposes ofexplanation only in describing the arrangement of the eye-mountableelectronic device 210. For example, the total thickness of theeye-mountable device 210 can be about 200 micrometers, while thethickness of the tear film layers 290, 292 can each be about 10micrometers, although this ratio may not be reflected in the drawings.Some aspects are exaggerated to allow for illustration and facilitateexplanation.

The eye 280 includes a cornea 282 that is covered by bringing the uppereyelid 286 and lower eyelid 288 together over the top of the eye 280.Incident light is received by the eye 280 through the cornea 282, wherelight is optically directed to light sensing elements of the eye 280(e.g., rods and cones, etc.) to stimulate visual perception. The motionof the eyelids 286, 288 distributes a tear film across the exposedcorneal surface 284 of the eye 280. The tear film is an aqueous solutionsecreted by the lacrimal gland to protect and lubricate the eye 280.When the eye-mountable device 210 is mounted in the eye 280, the tearfilm coats both the convex and concave surfaces 224, 226 with an innerlayer 290 (along the concave surface 226) and an outer layer 292 (alongthe convex layer 224). The tear film layers 290, 292 can be about 10micrometers in thickness and together account for about 10 microliters.

The tear film layers 290, 292 are distributed across the corneal surface284 and/or the convex surface 224 by motion of the eyelids 286, 288. Forexample, the eyelids 286, 288 raise and lower, respectively, to spread asmall volume of tear film across the corneal surface 284 and/or theconvex surface 224 of the eye-mountable device 210. The tear film layer290 on the corneal surface 284 also facilitates mounting theeye-mountable device 210 by capillary forces between the concave surface226 and the corneal surface 284. In some embodiments, the eye-mountabledevice 210 can also be held over the eye in part by vacuum forcesagainst the corneal surface 284 due to the concave curvature of theeye-facing concave surface 226.

As shown in the cross-sectional views in FIGS. 2c and 2d , the substrate230 can be inclined such that the flat mounting surfaces of thesubstrate 230 are approximately parallel to the adjacent portion of theconvex surface 224. As described above, the substrate 230 is a flattenedring with an inward-facing surface 232 (facing the concave surface 226of the polymeric material 220) and an outward-facing surface 234 (facingthe convex surface 224). The substrate 230 can have electroniccomponents and/or patterned conductive materials mounted to either orboth mounting surfaces 232, 234.

As shown in FIG. 2d , the bio-interactive electronics 260, thecontroller 250, the battery 255, and the conductive interconnects 251Aand 251B are located between the outward-facing surface 234 and theinward-facing surface 232 such that the bio-interactive electronics 260are facing the convex surface 224. As described above, the polymer layerdefining the anterior side may be greater than 50 micrometers thick,whereas the polymer layer defining the posterior side may be less than150 micrometers. Thus, the bio-interactive electronics 260 may be atleast 50 micrometers away from the convex surface 224 and may be agreater distance away from the concave surface 226. However, in otherexamples, the bio-interactive electronics 260 may be mounted on theinward-facing surface 232 of the substrate 230 such that thebio-interactive electronics 260 are facing the concave surface 226.Similarly, in other examples, the battery 255 may be located on theinward-facing surface 232 or the outward-facing surface 234 of thestructure 230. The bio-interactive electronics 260 and/or the battery255 could also be positioned closer to the concave surface 226 than theconvex surface 224. With this arrangement, the bio-interactiveelectronics 260 can receive analyte concentrations in the tear film 292through the channel 272, and the battery 255 can receive tear filmthrough the channel 274.

While the body-mountable device has been described as comprising theeye-mountable device 110 and/or the eye-mountable device 210, thebody-mountable device could comprise other mountable devices that aremounted on or in other portions of the human body.

For example, in some embodiments, the body-mountable device may comprisea tooth-mountable device. In some embodiments, the tooth-mountabledevice may take the form of or be similar in form to the eye-mountabledevice 110 and/or the eye-mountable device 210. For instance, thetooth-mountable device could include a polymeric material and/or polymerthat is the same as or similar to any of the polymeric materials orpolymers described herein and a substrate and/or structure that is thesame as or similar to any of the substrates or structures describedherein. With such an arrangement, the tooth-mountable device may beconfigured to detect at least one analyte in a fluid (e.g., saliva) of auser wearing the tooth-mountable device.

Moreover, in some embodiments, the body-mountable device may comprise askin-mountable device. In some embodiments, the skin-mountable devicemay take the form of or be similar in form to the eye-mountable device110 and/or the eye-mountable device 210. For instance, theskin-mountable device could include a polymeric material and/or apolymer that is the same as or similar to any of the polymeric materialsor polymers described herein and a substrate and/or structure that isthe same as or similar to any of the substrates or structures describedherein. With such an arrangement, the skin-mountable device may beconfigured to detect at least one analyte in a fluid (e.g.,perspiration, blood, etc.) of a user wearing the skin-mountable device.

Further, some embodiments may include privacy controls which may beautomatically implemented or controlled by the wearer of abody-mountable device. For example, where a wearer's collectedphysiological parameter data and health state data are uploaded to acloud computing network for trend analysis by a clinician, the data maybe treated in one or more ways before it is stored or used, so thatpersonally identifiable information is removed. For example, a user'sidentity may be treated so that no personally identifiable informationcan be determined for the user, or a user's geographic location may begeneralized where location information is obtained (such as to a city,ZIP code, or state level), so that a particular location of a usercannot be determined.

Additionally or alternatively, wearers of a body-mountable device may beprovided with an opportunity to control whether or how the devicecollects information about the wearer (e.g., information about a user'smedical history, social actions or activities, profession, a user'spreferences, or a user's current location), or to control how suchinformation may be used. Thus, the wearer may have control over howinformation is collected about him or her and used by a clinician orphysician or other user of the data. For example, a wearer may electthat data, such as health state and physiological parameters, collectedfrom his or her device may only be used for generating an individualbaseline and recommendations in response to collection and comparison ofhis or her own data and may not be used in generating a populationbaseline or for use in population correlation studies.

II. EXAMPLE METHODS

FIGS. 3a-d illustrate stages in a process for fabricating a battery,such as a battery 318 shown in FIGS. 3c and 3d . The illustrations shownin FIGS. 3a-d are generally shown in cross-sectional views to illustratesequentially formed layers developed to create the battery. The layerscan be developed by microfabrication and/or manufacturing techniquessuch as, for example, electroplating, photolithography, deposition,and/or evaporation fabrication processes and the like. The variousmaterials may be formed according to patterns using photoresists and/ormasks to pattern materials in particular arrangements. Additionally,electroplating techniques may also be employed to coat an arrangement ofelectrodes with a metallic plating. For example, an arrangement ofconductive material formed by a deposition and/or photolithographyprocess can be plated with a metallic material to create a conductivestructure with a desired thickness. However, the dimensions, includingrelative thicknesses and widths, of the various layers illustrated anddescribed in connection with FIGS. 3a-d to create the battery are notillustrated to scale. Instead, the drawings in FIGS. 3a-d schematicallyillustrate the ordering of the various layers for purposes ofexplanation only.

FIG. 3a illustrates forming a first electrode 302 on a structure 304 toprovide a partially-fabricated device 300 a. The first electrode 302 maydefine an anode of the battery 318.

The structure 304 may include a polymer 306 on which are formed acircuit 308, a sensor 310 and electrical interconnects 312A, 312B. Thestructure 304 may occupy a peripheral portion of a body-mountabledevice, such as body-mountable device 600 illustrated in FIG. 6. Thepolymer 306 may comprise a variety of polymeric materials, such asparalyene.

The circuit 308 can be configured in a variety of ways. As one example,the circuit 308 can comprise a chip including one or more logic elementsconfigured to operate the sensor 310. Other configurations of thecircuit 308 are possible as well.

The sensor 310 can be configured in a variety of ways. As one example,the sensor 310 may comprise a pair of electrodes, such as a workingelectrode and a reference electrode, configured to detect one or moreanalytes. Other configurations of the sensor 310 are possible as well.The sensor 310 can have a variety of thicknesses. As one example, thesensor 310 can have a thickness of 260 nanometers. Other thicknesses ofthe sensor 310 are possible as well.

The electrical interconnects 312A, 312B can be a variety of conductivematerials configured to electrically connect the circuit 308, the sensor310, and the battery 318. The electrical interconnects 312A, 312B mayinclude one or more layers of platinum, silver, gold, palladium,titanium, copper, chromium, nickel, aluminum, other metals or conductivematerials, and combinations thereof. In some embodiments, the electricalinterconnects 312A, 312B may include a substantially transparentconductive material for at least some components (e.g., a material suchas indium tin oxide).

The first electrode 302 may include a variety of materials. For example,the first electrode 302 may include at least one metal selected from thegroup consisting of zinc, iron, aluminum, an alloy that includes zincand magnesium, an alloy that includes iron and magnesium, and alloy thatincludes aluminum and magnesium. In addition, the first electrode 302may be formed in a variety of ways. For instance, first electrode 302may be formed as described with reference to FIGS. 4a -d.

In the illustrated example, the first electrode 302 may be formed on thestructure 304 when the structure 304 includes the circuit 308, thesensor 310, and the electrical interconnects 312A, 312B. However, inother examples, the first electrode 302 may be formed on the structurewhen the structure 304 may not include the circuit 308, the sensor 310,and/or the electrical interconnects 312A, 312B. As one example, thefirst electrode 302 may be formed on the structure 304 before thecircuit 308 may be mounted to the structure 304. As another example, thefirst electrode 302 may be formed on the structure 304 before the sensor310 may be formed on the structure 304. And as still another example,the first electrode 302 may be formed on the structure 304 before theelectrical interconnects 312A, 312B may be formed on the structure 304.

FIG. 3b illustrates forming a second electrode 314 on the structure 304to provide a partially-fabricated device 300 b. The second electrode 314may define a cathode of the battery 318. In addition, the secondelectrode 314 may be configured to reduce oxygen. In some examples, thereduced oxygen may be oxygen in the ambient air.

The second electrode 314 may include a variety of conductive materials.As one example, the second electrode 314 may include platinum. Inaddition, the second electrode 314 may be formed in a variety of ways.As one example, the second electrode 314 may be formed by amicrofabrication process such as sputtering. However, in other examples,the second electrode 314 may be formed by another microfabricationprocess such as evaporation.

In the illustrated example, the second electrode 314 may be formed onthe structure 304 when the structure 304 includes the circuit 308, thesensor 310, the electrical interconnects 312A, 312B, and the firstelectrode 302. However, in other examples, the second electrode 314 maybe formed on the structure when the structure 304 may not include thecircuit 308, the sensor 310, the electrical interconnects 312A, 312B,and/or the first electrode 302. As one example, the second electrode 314may be formed on the structure 304 before the circuit 308 may be mountedto the structure 304. As another example, the second electrode 302 maybe formed on the structure 304 before the sensor 310 may be formed onthe structure 304. As still another example, the second electrode 314may be formed on the structure 304 before the electrical interconnects312A, 312B may be formed on the structure 304. And as yet anotherexample, the second electrode 314 may be formed on the structure 304before the first electrode 302 may be formed on the structure 304.

FIG. 3c illustrates embedding the structure 304 in a polymer 316 toprovide a partially-fabricated device 300 c. The structure 304 may beembedded in the polymer 316 in a variety of ways. As one example, thepolymer 316 may be formed around the structure 304. With thisarrangement, the polymer 316 may cover the circuit 308, the sensor 310,the electrical interconnects 312A, 312B the first electrode 302, and thesecond electrode 314.

The polymer 316 may include one or more polymer layers, such as onepolymer layer or two polymer layers. Further, the polymer 316 mayinclude a variety of materials. For example, the polymer 316 may includea silicone hydrogel, polyhydroxyethylmethacrylate, and/or a siliconehydrogel.

In some examples, the first electrode 302 and the second electrode 314may be configured to use as an electrolyte fluid that has diffused intothe polymer 316. For instance, when a body-mountable device includes thefirst electrode 302, the second electrode 314, and the polymer 316, thefirst electrode 302 and the second electrode 314 may each be configuredto use as an electrolyte any bodily fluid of a wearer of thebody-mountable device that has diffused into the polymer 316. And insome such examples, the polymer 316 may include a silicone hydrogel orpolyhydroxyethylmethacrylate. With this arrangement, the battery 318 mayinclude the first electrode 302, the second electrode 314, and the fluidthat diffused into the polymer 318.

For example, when an eye-mountable device includes the first electrode302, the second electrode 314, and the polymer 316, the first electrode302 and the second electrode 314 may each be configured to use as anelectrolyte tear fluid that has diffused into the polymer 316. Asanother example, when a tooth-mountable device includes the firstelectrode 302, the second electrode 314, and the polymer 316, the firstelectrode 302 and the second electrode 314 may each be configured to useas an electrolyte saliva that has diffused into the polymer 316. As yetanother example, when a skin-mountable device includes the firstelectrode 302, the second electrode 314, and the polymer 316, the firstelectrode 302 and the second electrode 314 may each be configured to useas an electrolyte blood that has diffused into the polymer 316.

Further, in some examples, the first electrode 302 and the secondelectrode 314 may each be configured to use as an electrolyte fluid thatcontacts the first electrode 302 via one or more channels in the polymer316 and the second electrode 314 via one or more other channels in thepolymer 316. For instance, when a body-mountable device includes thefirst electrode 302, the second electrode 314, and the polymer 316, thefirst electrode 302 and the second electrode 314 may each be configuredto use an electrolyte any bodily fluid of a wearer of the body-mountabledevice that contacts the first electrode 302 via one or more channels inthe polymer 316 and the second electrode 314 via one or more otherchannels in the polymer 316. And in some such examples, the polymer 316may include a silicone elastomer. With this arrangement, the battery 318may include the first electrode 302, the second electrode 314, and thefluid that contacts the first electrode 302 via the one or more channelsand the second electrode 314 via the one or more other channels.

For example, when an eye-mountable device includes the first electrode302, the second electrode 314, and the polymer 316, the first electrode302 and the second electrode 304 may each be configured to use as anelectrolyte tear fluid that contacts the first electrode 302 via one ormore channels in the polymer 316 and the second electrode 314 via one ormore other channels in the polymer 316. As another example, when atooth-mountable device includes the first electrode 302, the secondelectrode 314, and the polymer 316, the first electrode 302 and thesecond electrode 314 may each be configured to use an electrolyte salivathat contacts the first electrode 302 via one or more channels in thepolymer 316 and the second electrode 314 via one or more other channelsin the polymer 316. As yet another example, when a skin-mountable deviceincludes the first electrode 302, the second electrode 314, and thepolymer 316, the first electrode 302 and the second electrode 314 mayeach be configured to use an electrolyte blood that contacts the firstelectrode 302 via one or more channels in the polymer 316 and the secondelectrode 314 via one or more other channels in the polymer 316.

FIG. 3d illustrates forming a first channel 320 to the first electrode302 through the polymer 316 and forming a second channel 322 to thesecond electrode 314 through the polymer 316 to provide apartially-fabricated device 300 d. The first channel 320 could be formedin a variety of ways. As one example, the first channel 320 may beformed by removing material from the polymer 316. The material from thepolymer 316 may be removed to form the first channel 320 in a variety ofways. For instance, the material from the polymer 316 may be removed toform the first channel 320 via process that includes drilling, ablation,etching, etc.

As another example, when embedding the structure 304 in the polymer 316includes forming the polymer 316 around the structure 304, a mask layermay be formed over the first electrode 302 before forming the polymer316 around the structure 304. With this arrangement, the polymer 316 maycover the mask layer. Further, in such an example, the mask layer may beremoved to form the first channel 320 to the first electrode 302. Themask layer may be removed in a variety of ways. For instance, the masklayer may be removed via a process that includes etching the mask layer,dissolving the mask layer in a fluid, and/or soaking the mask layer in afluid.

As still another example, when embedding the structure 304 in thepolymer 316 includes forming the polymer 316 around the structure, thefirst channel 320 may be molded. For instance, the polymer 316 may beformed in a molding piece that includes a protrusion that extends from asurface of the molding piece to the first electrode 302 through thepolymer 316 as the polymer 316 is being formed. With this arrangement,the protrusion may form the first channel 320 to the first electrode302.

Similarly, the second channel 322 could be formed in a variety of ways.For instance, the second channel 322 may be formed by any techniquesthat may be used to form the first channel 320 described herein. In someexamples, the second channel 322 may be formed by the same or similartechnique that may be used to the first channel 320. However, in otherexamples, the second channel 322 may be formed by a different techniquethan the technique that may be used to form the first channel 320.

Although partially-fabricated device 300 d has been described as forminga first channel 320 to the first electrode 302 and a second channel 322to the second electrode 314, in other examples one channel may be formedto both the first electrode 302 and the second electrode 314. With thisarrangement, a dimension of the one channel may be greater than or equalto a sum of a corresponding dimension of the first channel 320 and acorresponding dimension of the second channel 322. Such a channel may beformed by any of the techniques that may be used to form the firstchannel 320 and/or the second channel 322 described herein.

The battery 318 may be configured to provide electrical power to thecircuit 308. When the first electrode 302 includes zinc, the followingelectrochemical reaction may occur at the first electrode 302:Zn+H₂O→ZnO+2H⁺+2e ⁻

In addition, the following electrochemical reaction may occur at thesecond electrode 314:O₂+4e ⁻+4H⁺→2H₂O

As a result, a net chemical reaction of the battery 318 may be:2Zn+O₂→2ZnO

In some examples, one or more reaction products of the net chemicalreaction of the battery 318 (e.g., zinc oxide) may be insoluble underphysiological pH. As a result, at least one reaction product of the oneor more reaction products of the battery 318 may not disperse into thefluid that the battery 318 may be configured to use as the electrolyte.

For example, when an eye-mountable device includes the battery 318, atleast one reaction product of the one or more reaction products of thebattery 318 may not disperse into the tear fluid of the wearer of theeye-mountable device. As another example, when a tooth-mountable deviceincludes the battery 318, at least one reaction product of the one ormore reaction products of the battery 318 may not disperse into thesaliva of the wearer of the tooth-mountable device. As yet anotherexample, when a skin-mountable device includes the battery 318, at leastone reaction product of the one or more reaction products of the battery318 may not disperse into the blood of the wearer of the skin-mountabledevice.

One or more components of the battery 318 may have a variety of sizesand thicknesses. In some examples, when an eye-mountable device includesthe battery 318, the size and/or thicknesses of the one or morecomponents may be selected based on increasing battery capacity whileavoiding reducing a wearer's vision or comfort and avoiding reducingcommunication between an antenna (e.g., antenna 170 or loop antenna 270)and an external reader (e.g., external reader 180).

For example, when an eye-mountable device includes the battery 318, thesize and/or thicknesses of the first electrode 302 and/or the secondelectrode 314 may be selected based on increasing battery capacity whileavoiding reducing a wearer's vision or comfort and avoiding reducingcommunication between an antenna and an external reader. The size and/orthicknesses of the first electrode 302 and/or the second electrode 314may be selected based on other parameters as well, such as the type orcomposition of the fluid that the first electrode 302 and the secondelectrode 304 may each be configured to use as an electrolyte and thetype or properties of the material of the polymer 316.

As another example, when a skin-mountable device and/or atooth-mountable device includes the battery 318, the size and/orthicknesses of the first electrode 302 and/or the second electrode 314may be selected based on increasing battery capacity while avoidingreducing a wearer comfort and avoiding reducing communication between anantenna and an external reader. The size and/or thicknesses of the firstelectrode 302 and/or the second electrode 314 may be selected based onother parameters as well, such as the type or composition of the fluidthat the first electrode 302 and the second electrode 314 may each beconfigured to use as an electrolyte and the type or properties of thematerial of the polymer 316.

FIGS. 4a-d show stages of forming an electrode, such as an electrode 408shown in FIG. 4d . The illustrations shown in FIGS. 4a-d are generallyshown in cross-sectional views to illustrate sequentially formed layersto create the electrode. The layers can be developed by microfabricationand/or manufacturing techniques such as, for example, electroplating,photolithography, deposition, and/or evaporation fabrication processesand the like. The various materials may be formed according to patternsusing photoresists and/or masks to pattern materials in particulararrangements. Additionally, electroplating techniques may also beemployed to coat the electrode with a metallic plating. For example, anarrangement of conductive material formed by a deposition and/orphotolithography process can be plated with a metallic material tocreate a conductive structure with a desired thickness. However, thedimensions, including relative thicknesses and widths, of the variouslayers illustrated and described in connection with FIGS. 4a-d to createthe electrode are not illustrated to scale. Instead, the drawings inFIGS. 4a-d schematically illustrate the ordering of the various layersfor purposes of explanation only.

FIG. 4a illustrates forming a mixture 402. The mixture 402 may include ametal powder, a photopolymerizable monomer crosslinker, and aphotoinitiator. In some examples, the mixture 402 may comprise an ink.

The metal powder may take various different forms in various differentembodiments. For example, the metal powder may be in micro or nano form.In addition, the metal powder could include a variety of materials. Forexample, the metal powder may include at least one metal selected fromthe group consisting of zinc, iron, aluminum, an alloy that includeszinc and magnesium, an alloy that includes iron and magnesium, and alloythat includes aluminum and magnesium.

Moreover, the photopolymerizable monomer may include a variety ofmaterials. For example, the photopolymerizable monomer may include atleast one of methyl methacrylate, styrene, and cyclohexyl methacrylate.Further, the crosslinker may include a variety of materials. Forexample, the crosslinker may include difunctional polymerizable groups(e.g., ethylene dimethacrylate). Further still, the photoinitator mayinclude a variety of materials. For example, the photoinitatior mayinclude 2,2-Dimethoxy-2-phenylacetophenone.

FIG. 4b illustrates forming a metal layer 404 on the structure 304 toprovide a partially-fabricated device 400 b. For purposes ofexplanation, only a portion of the structure 304 is shown in FIGS. 4b-d. As shown in FIG. 4b , the structure 304 includes the polymer 306. Themetal layer may include a variety of conductive metals. For example, themetal layer may include one or more layers of gold. In addition, themetal layer may be formed in a variety of ways. As one example, themetal layer may be formed by a microfabrication process such assputtering. However, in other examples, the metal layer may be formed byanother microfabrication process such as evaporation.

FIG. 4c illustrates dispensing the mixture 402 onto the metal layer 404to provide a partially fabricated device 400 c. The mixture 402 may bedispensed onto the metal layer 404 in a variety of ways. For example,dispensing the mixture 402 onto the metal layer 404 may involve printingthe mixture 402 onto the metal layer 404. As another example, dispendingthe mixture 402 onto the metal layer 404 may involve injecting themixture 402 onto the metal layer 404.

FIG. 4d illustrates curing the mixture 402 on the metal layer 404 toform a crosslinked polymer layer 406 to provide a partially-fabricateddevice 400 d. With this arrangement, the crosslinked polymer layer 406and the metal layer 404 may define the electrode 408. In some examples,in the crosslinked polymer layer 408, at least a portion of the metalpowder is entrapped.

The mixture 402 may be cured in a variety of ways. As one example, themixture 402 may be cured with ultraviolet light. As another example, themixture 402 may be cured with heat.

In FIG. 3, the first electrode 302, the circuit 308, and the sensor 310,are each depicted as located on a surface (e.g., a top or bottomsurface) of the polymer 306. Similarly, in FIG. 4, the electrode 408 isdepicted as located on a surface (e.g., a top or bottom surface) of thepolymer 306. However, in other examples, one or more components may beembedded in a polymer of the structure 304 or surrounded by the polymer306, except for being exposed by an opening.

FIG. 5 illustrates an example structure 500, according to an exampleembodiment. The structure 500 includes a polymer 502, a circuit 504, afirst electrode 506, a second electrode 508, a sensor 510, electricalinterconnects 512A, 512B, a first opening 514, a second opening 516, anda third opening 518.

The polymer 502 may take the form of or be similar in form to thepolymer 306, the circuit 504 may take the form of or be similar in formto the circuit 308, the first electrode 506 may take the form of or besimilar in form to the first electrode 302, the second electrode 312 maytake the form of or be similar in form to the second electrode 314, thesensor 510 may take the form of or be similar in form to the sensor 310,and electrical interconnects 512A, 512B may take the form of or besimilar in form to electrical interconnects 312A, 312B.

As shown in FIG. 5, the circuit 504 may be embedded in the polymer 502;the first electrode 506 may be surrounded by the polymer 502, except forthe first electrode 506 being exposed by the first opening 514; thesecond electrode 508 may be surrounded by the polymer 502, except forthe second electrode 508 being exposed by the second opening 516; andthe sensor 510 may be surrounded by the polymer 502, except for thesensor 510 being exposed by the third opening 518.

In some examples, the polymer 502 may include a first polymer layer anda second polymer layer. In some such examples, the first polymer layermay be formed on the structure 500 before the circuit 504, the firstelectrode 506, the second electrode 508, and the sensor 510 are eachlocated on the structure 500. Further, in some such examples, the secondpolymer layer may be formed over the first polymer layer, the circuit504, the first electrode 506, the second electrode 508, and the senor510, and the electrical interconnects 512A, 512B. Further still, in somesuch examples, the first opening 514, the second opening 516, and thethird opening 518 may be formed after or while the second polymer layeris being formed.

The first opening 514 may be formed in a variety of ways. As oneexample, the first opening 514 may be formed by removing material fromthe second polymer layer. The material from the second polymer layer maybe removed to form the first opening 514 in a variety of ways. Forinstance, the material from the second polymer layer may be removed toform the first opening 514 via process that includes drilling, ablation,etching, etc.

As another example, a mask layer may be formed over the first electrode506 before forming the second polymer layer over the first electrode.With this arrangement, the second polymer layer may mold over the masklayer. Further, in such an example, the mask layer may be removed toform the first opening 514 to the first electrode 506. The mask layermay be removed in a variety of ways. For instance, the mask layer may beremoved via a process that includes etching the mask layer, dissolvingthe mask layer in a fluid, and/or soaking the mask layer in a fluid.

Similarly, the second opening 516 and the third opening 518 may beformed in a variety of ways. The second opening 516 and the thirdopening 518 may each be formed by any of the techniques that may be usedto form the first opening 514 as described herein. In some examples, thesecond opening 516 and/or the third opening 518 may be formed by thesame or similar technique that may be used to form the first opening514. However, in other examples, the second opening 516 and/or the thirdopening 518 may be formed by a different technique than the techniquethat may be used to form the first opening 514.

As noted, FIG. 6 illustrates the body-mountable device 600 fabricatedaccording to an example embodiment. The body-mountable device 600 mayinclude a first polymer layer 602, a second polymer 604, and a structure606 between the first polymer layer 602 and the second polymer layer604. As shown in FIG. 6, the structure 606 may be a ring-shapedsubstrate. The first polymer layer 602 may define a first side 608 ofthe body-mountable device 600, and the second polymer layer 604 maydefine a second side 610 of the body-mountable device.

The first polymer layer 602 and the second polymer layer 604 may takethe form of or be similar in form to the polymer 316, and the structure606 may take the form of or be similar in form to the structure 304.

The structure 606 may include a first electrode 612, a second electrode614, a circuit 616, and a sensor 618. The first electrode 612 may definean anode of a battery 620, and the second electrode 614 may define acathode of the battery 620 and may be configured to reduced oxygen. Thebattery 620 may be configured to provide electrical power to the circuit616.

The first electrode 612 may take the form of or be similar in form tothe first electrode 302 and/or the electrode 408, the second electrode614 may take the form of or be similar in form to the second electrode314, the circuit 616 may take the form of or be similar in form to thecircuit 308, the sensor 618 may take the form of or be similar in formto the sensor 310, and the battery 620 may take the form of or besimilar in form to the battery 318.

For instance, in some examples, the first electrode 612 may include atleast one metal selected from the group consisting of zinc, iron,aluminum, an alloy that includes zinc and magnesium, an alloy thatincludes iron and magnesium, and an alloy that includes aluminum andmagnesium. Further, in some examples, the second electrode 614 mayinclude platinum.

The body-mountable device 600 may further include a first channel 622 tothe first electrode 612 through the first polymer layer 602 or thesecond polymer layer 604 and a second channel 624 to the secondelectrode 614 through the first polymer layer 602 or the second polymerlayer 604. In the illustrated example, the first channel 622 to thefirst electrode 612 is through the second polymer layer 604 and thesecond channel 624 to the second electrode 614 is through the secondpolymer layer 604. However, in other examples, the first channel 622 tothe first electrode 612 may be through the first polymer layer 602and/or the second channel 624 to the second electrode 614 may be throughthe first polymer layer 602.

The first electrode 612 may be configured to use as an electrolyte fluidthat contacts the first electrode 612 via the first channel 622, and thesecond electrode 614 may be configured to use an electrolyte fluid thatcontacts the second electrode 614 via the second channel 624. And insome such examples, at least one of the first polymer layer 602 or thesecond polymer layer 604 may include a silicone elastomer. With thisarrangement, the battery 620 may include the first electrode 612, thesecond electrode 614, and the fluid that contacts the first electrode612 via the first channel 622 and the second electrode 614 via thesecond channel 624.

The first electrode 612 may be configured to use as an electrolyte anybodily fluid of a wearer of the body-mountable device 600 that contactsthe first electrode 612 via the first channel 622, and the secondelectrode 614 may be configured to use as an electrolyte any bodilyfluid of the wearer of the body-mountable device that contacts thesecond electrode 614 via the second channel 624. For example, when thebody-mountable device 600 comprises an eye-mountable device, the firstelectrode 612 may be configured to use as an electrolyte tear fluid thatcontacts the first electrode 612 via the first channel 622, and thesecond electrode 614 may be configured to use as an electrolyte tearfluid that contacts the second electrode 614 via the second channel 624.As another example, when the body-mountable device 600 comprises atooth-mountable device, the first electrode 612 may be configured to useas an electrolyte saliva that contacts the first electrode 612 via thefirst channel 622, and the second electrode 614 may be configured to useas an electrolyte saliva that contacts the second electrode 614 via thesecond channel 624. As yet another example, when the body-mountabledevice 600 comprises a skin-mountable device, the first electrode 612may be configured to use as an electrolyte blood that contacts the firstelectrode 612 via the first channel 622, and the second electrode 614may be configured to use as an electrolyte blood that contacts thesecond electrode 614 via the second channel 624.

The first channel 622 to the first electrode 612 may take the form of orbe similar in form to the first channel 320 to the first electrode 302,and the second channel 624 to the second electrode 614 may take the formof or be similar in form to the second channel 322 to the secondelectrode 312.

The location of the first channel 622 may be based on a location of thefirst electrode 612 on the structure 606. As one example, when the firstelectrode 612 is formed on a surface of the structure 606 that is facingthe first side 608 of the body-mountable device 600, the first channel622 may be located through the first polymer layer 602. As anotherexample, when the first electrode 612 is formed on a surface of thestructure 606 that is facing the second side 610 of the body-mountabledevice 600, the first channel 622 may be located through the secondpolymer layer 604.

Similarly, the location of the second channel 624 may be based on alocation of the second electrode 614 on the structure 606. As oneexample, when the second electrode 614 is formed on a surface of thestructure 606 that is facing the first side 608 of the body-mountabledevice 600, the second channel 624 may be located through the firstpolymer layer 602. As another example, when the second electrode 614 isformed on a surface of the structure 606 that is facing the second side610 of the body-mountable device 600, the second channel 624 may belocated through the second polymer layer 604.

Moreover, in some examples, the first polymer layer 602 or the secondpolymer layer 604 may have one channel to the first electrode 612 andthe second electrode 614. Further, in some such examples, a dimension ofthe one channel may be greater than or equal to a sum of a correspondingdimension of the first channel 622 and a corresponding dimension of thesecond channel 624.

The material of the first polymer layer 602 and/or the second polymerlayer 604 may be selected based on the location of the first channel 622and/or the second channel 624. As one example, when the first channel622 or the second channel 624 is through the first polymer layer 602,the first polymer layer 602 may include a silicone elastomer. As anotherexample, when the first channel 622 or the second channel 624 is throughthe first polymer layer 604, the second polymer layer 604 may include asilicone elastomer.

Further, in some examples, the first electrode 612 and the secondelectrode 614 may each be configured to use as an electrolyte fluid thathas diffused into the first polymer layer 602 or the second polymerlayer 604. And in some such examples, at least one of the first polymerlayer 602 or the second polymer layer 604 may include a siliconehydrogel or polyhydroxyethylmethacrylate. With this arrangement, thebattery 620 may include the first electrode 612, the second electrode614, and the fluid that has diffused into the first polymer layer 602 orthe second polymer layer 604. Accordingly, with this arrangement, thebody-mountable device 600 might not include the first channel 622 and/orthe second channel 624.

The first electrode 612 and the second electrode 614 may each beconfigured to use as an electrolyte any bodily fluid of a wearer of thebody-mountable device 600 that has diffused into the first polymer layer602 or the second polymer layer 604. For example, when thebody-mountable device 600 comprises an eye-mountable device, the firstelectrode 612 and the second electrode 614 may each be configured to useas an electrolyte tear fluid that has diffused into the first polymerlayer 602 or the second polymer layer 604. As another example, when thebody-mountable device 600 comprises a tooth-mountable device, the firstelectrode 612 and the second electrode 614 may each be configured to useas an electrolyte saliva that has diffused into the first polymer layer602 or the second polymer layer 604. As yet another example, when thebody-mountable device 600 comprises a skin-mountable device, the firstelectrode 612 and the second electrode 614 may each be configured to useas an electrolyte blood that has diffused into the first polymer layer602 or the second polymer layer 604.

Further still, in some examples, the material of the first polymer layer602 and/or the second polymer layer 604 may be based on a location ofthe first electrode 612 on the structure and/or a location of the secondelectrode 614 on the structure 606. As one example, when the firstelectrode 612 and/or the second electrode 614 is formed on a surface ofthe structure 606 that is facing the first side 608 of thebody-mountable device 600, the first polymer layer 602 may include asilicone hydrogel or polyhydroxyethylmethacrylate. As another example,when the first electrode 612 and/or the second electrode 614 is formedon a surface of the structure 606 that is facing the second side 610 ofthe body-mountable device 600, the second polymer layer 604 may includea silicone hydrogel or polyhydroxyethylmethacrylate.

Moreover, in some examples, the first electrode 612 may be configured touse as an electrolyte fluid that has diffused into the first polymerlayer 602 or the second polymer layer 604, and the second electrode 614may be configured to use as an electrolyte fluid that contacts thesecond electrode 614 via the second channel 624. With this arrangement,the battery 620 may include the first electrode 612, the secondelectrode 614, the fluid that has diffused into the first polymer layer602 or the second polymer layer 604, and the fluid that contacts thesecond electrode 614 via the second channel 624. Accordingly, with thisarrangement, the body-mountable device 600 might not include the firstchannel 622.

Further, in some examples, the first electrode 612 may be configured touse as an electrolyte fluid that contacts the first electrode 612 viathe first channel 622, and the second electrode 614 may be configured touse as an electrolyte fluid that has diffused into the first polymerlayer 602 or the second polymer layer 604. With this arrangement, thebattery 620 may include the first electrode 612, the second electrode614, the fluid that contacts the first electrode 612 via the firstchannel 622, and the fluid that has diffused into the first polymerlayer 602 or the second polymer layer 604. Accordingly, with thisarrangement, the body-mountable device 600 might not include the secondchannel 624.

In another aspect, in the illustrated example, the second polymer layer604 further includes a channel 626 to the sensor 618. With thisarrangement, the sensor 618 may receive an analyte via the channel 626.

As noted, the battery 620 may be configured to provide electrical powerto the circuit 616. With this arrangement, the battery 620 may permitautonomous operation of the body-mountable device 600. For example, thebattery 620 may bias the sensor 618, via a potentiostat, so thatelectrodes in the sensor 618 are at appropriate potentials for analytemeasurement. The battery 620 may provide electrical power to otherinterfaces for the sensor 618 as well. As another example, the battery620 may power a memory in the circuit 618, for data logging of sensorreadings from the sensor 618.

The battery 620 may also be configured to provide electrical power to avariety of other circuits that may be located on the structure 606, suchas a computation circuit, a communication circuit, and/or a displaycircuit. Further, in some examples, the battery 620 may be configured toprovide electrical power to one or more low-power circuits.

In addition, the battery 620 may also be configured to provideelectrical power to other components located on the structure 606. Asone example, the battery 620 may be configured to provide electricalpower to one or more indicators located on the structure, such as apixel array. With this arrangement, the one or more indicators may beconfigured to provide feedback to a wearer of the body-mountable device.As another example, the battery 620 may be configured to provideelectrical power to a camera and/or a video camera that may be locatedon the structure 606. Further, in some examples, the battery 620 may beconfigured to provide electrical power to one or more peripheralcomponents.

In some examples, the battery 620 may be configured to be recharged byan antenna located on the structure 606. For instance, the battery 620may be configured to be recharged by radio frequency radiation harvestedby the antenna. With this arrangement, the battery 620 may be wirelesslyrecharged.

Although the battery 620 is described above as including the firstelectrode 612 and the second electrode 614, in other examples a batteryused in the body-mountable device 600 may include a solid-state device.And in some such examples, the battery may include anode that includeslithium.

Further, in some such examples, the battery may be mounted to thestructure 606. For instance, the battery may be flip-chip bonded to thestructure 606 using anisotropic conductive paste (ACP). In an examplewhere the battery includes a solid-state device, the battery may bemounted to the structure 606 before, after, or while the circuit 616 maybe mounted to the structure 606.

Such a battery may be configured to provide electrical power provideelectrical power to the circuit 616. With this arrangement, the batterymay permit autonomous operation of the body-mountable device 600. Forexample, the battery may bias the sensor 618, via a potentiostat, sothat electrodes in the sensor 618 are at appropriate potentials foranalyte measurement. The battery may provide electrical power to otherinterfaces for the sensor 618 as well. As another example, the batterymay power a memory in the circuit 618, for data logging of sensorreadings from the sensor 618.

The battery may also be configured to provide electrical power to avariety of other circuits that may be located on the structure 606, suchas a computation circuit, a communication circuit, and/or a displaycircuit. Further, in some examples, the battery may be configured toprovide electrical power to one or more low-power circuits.

In addition, the battery may also be configured to provide electricalpower to other components located on the structure 606. As one example,the battery may be configured to provide electrical power to one or moreindicators located on the structure, such as a pixel array. With thisarrangement, the one or more indicators may be configured to providefeedback to a wearer of the body-mountable device. As another example,the battery may be configured to provide electrical power to a cameraand/or a video camera that may be located on the structure 606. Further,in some examples, the battery may be configured to provide electricalpower to one or more peripheral components.

In some examples, the battery may be configured to be recharged by anantenna located on the structure 606. For instance, the battery may beconfigured to be recharged by radio frequency radiation harvested by theantenna. With this arrangement, the battery may be wirelessly recharged.

Further, although the battery 620 has been described as included in thebody-mountable device 600, in other examples the battery 620 may beincluded in other devices. For example, the battery 620 may be includedin an implantable device that may be implanted, for example, in thehuman body. Such implantable devices may take the form of or be similarin form to the body-mountable device 600. As another example, thebattery 620 may be included in a device that may not be mounted on awearer or implanted in the wearer. Such devices may be take the form ofor be similar in form to the body-mountable device 600.

FIG. 7 is a flowchart of a method 700 for fabricating a battery,according to an example embodiment. The method 700 may involve forming afirst electrode on a structure (block 702). The first electrode maydefine an anode of a battery. Further, the battery may be configured toprovide electrical power to a circuit located on the structure.

The first electrode may take the form of or be similar in form the firstelectrode 302, the structure may take the form of or be similar in formto the structure 304 or the structure 500, and the battery may take theform of or be similar in form to the battery 318. For instance, in someembodiments, the first electrode may include at least one metal selectedfrom the group consisting of zinc, iron, aluminum, an alloy thatincludes zinc and magnesium, an alloy that includes iron and magnesium,and an alloy that includes aluminum and magnesium. Further, the firstelectrode may be formed the same or similar way as the first electrode302 may be formed as described with reference to FIG. 3 a.

The method 700 may involve forming a second electrode on the structure(block 704). The second electrode may define a cathode of the battery.Further, the second electrode may be configured to reduce oxygen.

The second electrode may take the form of or be similar in form to thesecond electrode 314. For instance, in some embodiments, the secondelectrode may include platinum. Further, the second electrode may beformed the same or similar way as the second electrode 314 may be formedas described with reference to FIG. 3b . For instance, in someembodiments, the second electrode may be formed by sputtering orevaporation.

The method 700 may involve embedding the structure in a polymer (block706). The polymer may take the form of or be similar in form to thepolymer 316. For instance, the polymer may include a silicone hydrogel,polyhydroxyethylmethacrylate, or a silicone elastomer. Further, thestructure may be embedded in the polymer the same or similar way as thestructure 304 is embedded in the polymer 316 as described with referenceto FIG. 3 c.

In some embodiments, the first electrode may be configured to use as anelectrolyte fluid that contacts the first electrode via a first channel,and the second electrode may be configured to use as an electrolytefluid that contacts the second electrode via a second channel. And in atleast one such embodiment, the method 700 may further involve formingthe first channel to the first electrode through the polymer, andforming the second channel to the second electrode through the polymer.Further, in at least one such embodiment, the polymer may include asilicone elastomer.

The first channel to the first electrode may take the form of or besimilar in form to the first channel 320 to the first electrode 302, andthe second channel to the second electrode may take the form of or besimilar in form to the second channel 322 to the second electrode 314.Further, the first channel to the first electrode may be formed the sameor similar way as the first channel 320 to the first electrode 302 maybe formed as described with reference to FIG. 3d . Further still, thesecond channel the second electrode may be formed the same or similarway as the second channel 322 to the second electrode 314 may be formedas described with reference to FIG. 3 d.

In some embodiments, the first and second electrodes may each beconfigured to use as an electrolyte fluid that has diffused into thepolymer. And in at least one such embodiment, the polymer may include asilicone hydrogel or polyhydroxyethylmethacrylate.

FIG. 8 is a flowchart of a method 800 for fabricating an electrode,according to an example embodiment. The method 800 may be performed inconnection with block 702 of method 700. The method 800 may involveforming a mixture (block 802). The mixture may include a metal powder, aphotopolymerizable monomer, a crosslinker, and a photoinitiator. Themixture may take the form of or be similar in form to the mixture 402.For instance, in at least one embodiment, the mixture may comprise anink. Further, the mixture may be formed the same or similar way as themixture 402 may be formed as described with respect to FIG. 4 a.

The method 800 may involve forming a metal layer on the structure (block804). The metal layer may take the form of or be similar in form to themetal layer 404, and the structure may take the form of or be similar inform to the structure 304. Further, the metal layer may be formed on thestructure the same or similar way as the metal layer 404 may be formedon the structure 304 as described with reference to FIG. 4 b.

The method 800 may involve dispensing the mixture onto the metal layer(block 806). The mixture may be dispensed onto the metal layer the sameor similar was as the mixture 402 may be dispensed onto the metal layer404 as described with reference to FIG. 4c . For instance, in at leastone embodiment, dispensing the mixture onto the metal layer may involveprinting the mixture onto the metal layer.

The method 800 may involve curing the mixture on the metal layer to forma crosslinked polymer layer (block 806). In the crosslinked polymerlayer, at least a portion of the metal powder may be entrapped. Thecrosslinked polymer layer may take the form of or be similar in form tothe crosslinked polymer layer 406. Further, the mixture may be cured toform the crosslinked polymer layer the same or similar way as themixture 402 may be cured to form the crosslinked polymer layer 406 asdescribed with reference to FIG. 4 d.

FIG. 9 depicts a computer-readable medium configured according to anexample embodiment. In example embodiments, the example system caninclude one or more processors, one or more forms of memory, one or moreinput devices/interfaces, one or more output devices/interfaces, andmachine-readable instructions that when executed by the one or moreprocessors cause a system to carry out the various functions, tasks,capabilities, etc., described above.

In some embodiments, the disclosed techniques can be implemented bycomputer program instructions encoded on a non-transitorycomputer-readable storage media in a machine-readable format, or onother non-transitory media or articles of manufacture. FIG. 9 is aschematic illustrating a conceptual partial view of a computer programproduct 900 that includes a computer program for executing a computerprocess on a computing device, to perform any of the methods describedherein.

In one embodiment, the computer program product 900 is provided using asignal bearing medium 902. The signal bearing medium 902 may include oneor more programming instructions 904 that, when executed by one or moreprocessors may provide functionality or portions of the functionalitydescribed above with respect to FIGS. 7-8. In some examples, the signalbearing medium 902 can include a non-transitory computer-readable medium906, such as, but not limited to, a hard disk drive, a Compact Disc(CD), a Digital Video Disk (DVD), a digital tape, memory, etc. In someimplementations, the signal bearing medium 902 can be a computerrecordable medium 908, such as, but not limited to, memory, read/write(R/W) CDs, R/W DVDs, etc. In some implementations, the signal bearingmedium 902 can be a communications medium 910, such as, but not limitedto, a digital and/or an analog communication medium (e.g., a fiber opticcable, a waveguide, a wired communications link, a wirelesscommunication link, etc.). Thus, for example, the signal bearing medium902 can be conveyed by a wireless form of the communications medium 910.

The one or more programming instructions 904 can be, for example,computer executable and/or logic implemented instructions. In someexamples, a computing device is configured to provide variousoperations, functions, or actions in response to the programminginstructions 904 conveyed to the computing device by one or more of thecomputer readable medium 906, the computer recordable medium 908, and/orthe communications medium 910.

The non-transitory computer readable medium 906 can also be distributedamong multiple data storage elements, which could be remotely locatedfrom each other. The computing device that executes some or all of thestored instructions can be a microfabrication controller, or anothercomputing platform. Alternatively, the computing device that executessome or all of the stored instructions could be remotely locatedcomputer system, such as a server.

IV. CONCLUSION

It should be understood that arrangements described herein are forpurposes of example only. As such, those skilled in the art willappreciate that other arrangements and other elements (e.g., machines,interfaces, functions, orders, and groupings of functions, etc.) can beused instead, and some elements may be omitted altogether according tothe desired results. Further, many of the elements that are describedare functional entities that may be implemented as discrete ordistributed components or in conjunction with other components, in anysuitable combination and location.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims, along with the fullscope of equivalents to which such claims are entitled. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting.

Where example embodiments involve information related to a person or adevice of a person, some embodiments may include privacy controls. Suchprivacy controls may include, at least, anonymization of deviceidentifiers, transparency and user controls, including functionalitythat would enable users to modify or delete information relating to theuser's use of a product.

Further, in situations in where embodiments discussed herein collectpersonal information about users, or may make use of personalinformation, the users may be provided with an opportunity to controlwhether programs or features collect user information (e.g., informationabout a user's medical history, social network, social actions oractivities, profession, a user's preferences, or a user's currentlocation), or to control whether and/or how to receive content from thecontent server that may be more relevant to the user. In addition,certain data may be treated in one or more ways before it is stored orused, so that personally identifiable information is removed. Forexample, a user's identity may be treated so that no personallyidentifiable information can be determined for the user, or a user'sgeographic location may be generalized where location information isobtained (such as to a city, ZIP code, or state level), so that aparticular location of a user cannot be determined. Thus, the user mayhave control over how information is collected about the user and usedby a content server.

What is claimed is:
 1. A method comprising: forming a first electrode ona structure, wherein the first electrode defines an anode of a batterythat uses tear fluid as an electrolyte; forming a second electrode onthe structure, wherein the second electrode defines a cathode of thebattery, and wherein the second electrode reduces oxygen; and embeddingthe structure in a polymer, wherein the polymer defines a first side anda second side of an eye-mountable device, wherein the battery producesat least one reaction product, and wherein the at least one reactionproduct is insoluble under physiological pH, such that the at least onereaction product does not disperse into the tear fluid.
 2. The method ofclaim 1, wherein the tear fluid is able to contact the first and secondelectrodes by diffusion through the polymer.
 3. The method of claim 2,wherein the polymer comprises a silicone hydrogel orpolyhydroxyethylmethacrylate.
 4. The method of claim 1, wherein themethod further comprises: forming a first channel to the first electrodethrough the polymer, wherein the tear fluid is able to contact the firstelectrode via the first channel; and forming a second channel to thesecond electrode through the polymer, wherein the tear fluid is able tocontact the second electrode via the second channel.
 5. The method ofclaim 4, wherein the polymer comprises a silicone elastomer.
 6. Themethod of claim 1, wherein the first electrode comprises at least onemetal selected from the group consisting of zinc, iron, aluminum, analloy that includes zinc and magnesium, an alloy that includes iron andmagnesium, and an alloy that includes aluminum and magnesium.
 7. Themethod of claim 1, wherein the second electrode comprises platinum. 8.The method of claim 1, wherein forming the first electrode comprises:forming a mixture that comprises a metal powder, a photopolymerizablemonomer, a crosslinker, and a photoinitiator; forming a metal layer onthe structure; dispensing the mixture onto the metal layer; and curingthe mixture on the metal layer to form a crosslinked polymer layer inwhich at least a portion of the metal powder is entrapped.
 9. The methodof claim 8, wherein the mixture comprises an ink.
 10. The method ofclaim 8, wherein dispensing the mixture onto the metal layer comprisesprinting the mixture onto the metal layer.
 11. The method of claim 1,wherein forming the second electrode comprises forming the secondelectrode by sputtering or evaporation.
 12. An eye-mountable devicecomprising: a first polymer layer defining a first side of theeye-mountable device; a second polymer layer defining a second side ofthe eye-mountable device; and a structure between the first and secondpolymer layers, wherein the structure comprises: a first electrode,wherein the first electrode defines an anode of a battery that uses tearfluid as an electrolyte, and a second electrode, wherein the secondelectrode defines a cathode of the battery, wherein the second electrodereduces oxygen, wherein the battery produces at least one reactionproduct, and wherein the at least one reaction product is insolubleunder physiological pH, such that the at least one reaction product doesnot disperse into the tear fluid.
 13. The eye-mountable device of claim12, wherein the tear fluid is able to contact the first and secondelectrodes by diffusion through the first polymer layer or the secondpolymer layer.
 14. The eye-mountable device of claim 12, wherein thefirst polymer layer or the second polymer layer comprises a siliconehydrogel or polyhydroxyethyl methacrylate.
 15. The eye-mountable deviceof claim 12 further comprising: a first channel to the first electrodethrough the first polymer layer or second polymer layer, wherein thetear fluid is able to contact the first electrode via the first channel;and a second channel to the second electrode through the first polymerlayer or second polymer layer, wherein the tear fluid is able to contactthe second electrode via the second channel.
 16. The eye-mountabledevice of claim 12, wherein the first polymer or the second polymercomprises a silicone elastomer.
 17. The eye-mountable device of claim12, wherein the first electrode comprises at least one metal selectedfrom the group consisting of zinc, iron, aluminum, an alloy thatincludes zinc and magnesium, an alloy that includes iron and magnesium,and an alloy that includes aluminum and magnesium.
 18. The eye-mountabledevice of claim 12, wherein the second electrode comprises platinum.